Spin torque transfer technology, also referred to as spin electronics, combines semiconductor technology and magnetics, and is a more recent development. In spin electronics, the spin of an electron, rather than the charge, is used to indicate the presence of digital information. The digital information or data, represented as a “0” or “1”, is storable in the alignment of magnetic moments within a magnetic element. The resistance of the magnetic element depends on the moment's alignment or orientation. The stored state is read from the element by detecting the component's resistive state.
The magnetic element, in general, includes a ferromagnetic pinned layer and a ferromagnetic free layer, each having a magnetization orientation that defines the resistance of the overall magnetic element. Such an element is generally referred to as a “spin tunneling junction,” “magnetic tunnel junction”, “magnetic tunnel junction cell”, and the like. When the magnetization orientations of the free layer and pinned layer are parallel, the resistance of the element is low. When the magnetization orientations of the free layer and the pinned layer are antiparallel, the resistance of the element is high.
Application of spin torque transfer memory has a switching current density requirement generally at 106 to 107 A/cm2, which leads to difficulty in integrating with a regular CMOS process. It is desirable to reduce the switching current density significantly in order to make a feasible product.
Various bilayer heat-assisted media designs have been proposed that attempt to lower the coercivity of the bilayer media and reduce the switching field. However, there are major difficulties in implementing these types of assisted switching. First, the reliability of the spin torque memory is a concern when heat assistance is utilized, due to the heat generated during switching; the assist temperature has the potential to thermally degrade the magnetic layers of the spin torque memory. This high transition temperature may have adverse thermal effects to the memory system, as the high power consumption needed during write cycles produces large amounts of heat that need to be dissipated.
Other designs of assisted switching are needed.